Foramen magnum meningioma classification

Based on the compartment of development FMMs can be classified in intradural, extradural or intra- and extradural. Most of the time, FMMs are strictly intradural. Ten percent have an extradural extension, then they are intra- and extradural, and a few may be entirely extradural 1). 2) 3)

Petroclival and foramen magnum meningiomas are classified according to their tumor Equivalent Diameter.

The compartment of development was most of the time intradural (101/107, 94.4%) and less frequently extradural (3/107, 2.8%) or both intra-extradural. (3/107, 2.8%). When developed inside the intradural compartment, FMMs were subdivided into posterior (6/104, 5.8%), lateral (57/104, 54.8%), and anterior (41/104, 39.4%), if their insertion was respectively posterior to the denticulate ligament, anterior to the dentate ligament without or with extension over the midline. Anterior and lateral intradural lesions grew below (77/98, 78.6%), above (16/98, 16.3%), or on both sides (5/98, 5.1%) of the VA. Only three cases of extraduralFMMs (3/107, 2.8%) were resected by an antero-lateral approach while all the other ones (104/107, 97.2%) were removed successfully by a postero-lateral approach. Lower cranial nerves were displaced superiorly in FMM growing below the VA but their position cannot be anticipated in other situations.

This classification system helps for defining the best surgical approach but also for anticipating the position of the lower cranial nerves and therefore for reducing the surgical morbidity 4).

George B, Lot G, Boissonnet H. Meningioma of the foramen magnum: a series of 40 cases. Surg Neurol. 1997;47(4):371–9.
Bruneau M, George B. Foramen magnum meningiomas: detailed surgical approaches and technical aspects at Lariboisière Hospital and review of the literature. Neurosurg Rev. 2008;31(1):19–33.
Goel A, Desai K, Muzumdar D. Surgery on anterior foramen magnum meningiomas using a conventional posterior suboccipital approach: a report on an experience with 17 cases. Neurosurgery. 2001;49(1):102–7.
Bruneau M, George B. Classification system of foramen magnum meningiomas. J Craniovertebr Junction Spine. 2010 Jan;1(1):10-7. doi: 10.4103/0974-8237.65476. PubMed PMID: 20890409; PubMed Central PMCID: PMC2944858.
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